package com.wc.codeforces.思维.Kachina_s_Favorite_Binary_String;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/11/17 23:37
 * @description
 * https://codeforces.com/contest/2037/problem/E
 */
public class Main {
    /**
     * 特殊情况 sum = 0, 不满足的
     * 找到最后一个 1, 前面如果等于0了, 一定可以计算到
     */
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 10010;
    static char[] cs = new char[N];
    static int n;

    public static void main(String[] args) {
        int T = sc.nextInt();
        while (T-- > 0){
            n = sc.nextInt();
            out.println("? " + 1 + " " + n);
            out.flush();
            int sum = sc.nextInt();
            if (n == 2){
                if (sum == 1) out.println("! 01");
                else out.println("! IMPOSSIBLE");
                out.flush();
                continue;
            }
            if (sum == 0) {
                out.println("! IMPOSSIBLE");
                out.flush();
                continue;
            }
            int pre0 = -1;
            for (int i = n - 1; i >= 2; i--){
                out.println("? " + 1 + " " + i);
                out.flush();
                int cnt = sc.nextInt();
                if (cnt == sum) {
                    cs[i + 1] = '0';
                    pre0--;
                } else {
                    cs[i + 1] = '1';
                    pre0 = sum - cnt;
                }
                sum = cnt;
                // 1111 0000 1 00
                if (sum == 0) {
                    while (pre0 > 0 && i > 2) {
                        cs[i--] = '0';
                        pre0--;
                    }
                    while (i > 2) cs[i--] = '1';
                    break;
                }
            }
            if (sum == 1) {
                cs[1] = '0';
                cs[2] = '1';
            } else if (pre0 == 2) cs[1] = cs[2] = '0';
            else if (pre0 == 0) cs[1] = cs[2] = '1';
            else {
                cs[1] = '1';
                cs[2] = '0';
            }

            out.println("! " + new String(cs, 1, n));
            out.flush();
        }
    }
}
class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}

